I love the Coopers APA kit, for a 1-can kit I was consistently impressed with the end result. I used to add 500g of light hopped spraymalt and 500g unrefined cane sugar only and it was often praised by my friends.
I love the idea of splitting a 5 gallon batch down into several smaller batches and treating them differently, I hadn't thought of that but its an excellent idea. You must get a really clear idea of what different additions make to the final beer that way.
DKM